Sheet discharging apparatus and image forming apparatus

Abstract

To provide a sheet discharging apparatus which can increase the number of sheets which can be loaded into a loading section, and to provide an image formation apparatus including the sheet discharging apparatus.SOLUTION: A sheet discharging apparatus includes a discharging section configured to discharge sheets, a loading section into which the sheets discharged from the discharging section are loaded, a moving member configured to contact with the sheet loaded into the loading section and move to a first position, a second position, and a third position which is spaced apart from the first position farther than the second position, a detection section configured to detect a position of the moving member, and a control section configured to control the discharging section. The moving member is moved from the first position to the second position and the third position by increase of a height of the sheets loaded into the loading section. The control section controls the discharging section in a first mode in which discharge of the sheets by the discharging section is restricted when the detection section detects the moving member reaching the second position or a second mode in which the discharge of the sheet by the discharging section can continue even in a state that the moving member is located between the second position and the third position.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a sheet discharging device that discharges a sheet and an image forming apparatus including the same. [Background technology]

[0002] Conventionally, an image forming apparatus has been proposed that has a load amount detection device that detects the load amount of sheets discharged from a discharge port and stacked on an external tray (see Patent Document 1). The load amount detection device is provided above the pair of discharge rollers, and has an optical sensor, an arm-shaped rotor that extends from a rotating shaft into a paper discharge space, and an arm-shaped detector that extends upward from the rotating shaft. When the rotor is pushed upward by the sheets stacked on the external tray, the detector also rotates around the rotating shaft. When the stack height of the sheets stacked on the horizontal loading surface of the external tray reaches a predetermined height or more, the detector retracts from the optical path of the optical sensor, and the signal level of the optical sensor changes from LOW to HIGH. When the signal level from the optical sensor remains HIGH, the control unit of the image forming apparatus determines that the sheets on the horizontal loading surface of the external tray have reached the maximum load amount, and interrupts the printing operation.

[0003] Furthermore, when a sheet larger than A4 size is printed, the control unit counts the number of printed sheets. When the count value of the number of printed sheets reaches a threshold value T, the control unit determines that the amount of sheets stacked on the inclined loading surface of the external tray has reached the maximum amount, and stops driving the pair of discharge rollers with the sheet sandwiched between them. This keeps the detector in the retracted position, and keeps the signal level of the optical sensor HIGH. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-121826 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the load amount detection device described in Patent Document 1, when sheets larger than A4 size are printed, the signal level of the optical sensor is kept HIGH and the printing operation is interrupted based on the count value of the number of printed sheets reaching a threshold value T. In other words, when the signal level of the optical sensor becomes HIGH, the printing operation is immediately interrupted. However, depending on the type of sheet to be discharged, for example, there are cases where the sheet can be discharged to the external tray even if the signal level of the optical sensor becomes HIGH, and there is room for improvement in the number of sheets that can be stacked on the external tray.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a sheet ejection device capable of increasing the number of sheets that can be stacked on a stacking section, and an image forming apparatus including the same. [Means for solving the problem]

[0007] The present invention provides a sheet discharge device comprising a discharge section that discharges sheets, a loading section that stacks the sheets discharged by the discharge section, a movable member that can contact the sheets loaded on the loading section and is movable to a first position, a second position, and a third position that is farther from the first position than the second position, a detection section that detects the position of the movable member, and a control section that controls the discharge section, wherein the movable member moves from the first position toward the second position and the third position as the height of the sheets loaded on the loading section increases, and the control section controls the discharge section in a first mode that restricts the discharge of sheets by the discharge section when the detection section detects that the moving member has reached the second position, and in a second mode that allows the discharge section to continue discharging sheets even when the moving member is located between the second position and the third position. Effect of the Invention

[0008] According to the present invention, the number of sheets that can be stacked on the stacking section can be increased. [Brief description of the drawings]

[0009] [Figure 1] 1 is an overall schematic view showing a printer according to a first embodiment. [Diagram 2] FIG. [Diagram 3] 4A is a cross-sectional view showing a full-load detection member located at a standby position, and FIG. 4B is a cross-sectional view showing a full-load detection member and a full-load detection sensor located at the standby position. [Figure 4] 4A is a cross-sectional view showing a full-load detection member located at a detection position, and FIG. 4B is a cross-sectional view showing a full-load detection member and a full-load detection sensor located at the detection position. [Diagram 5] FIG. 2 is a block diagram showing a control block of the printer. [Figure 6] FIG. 4 is a diagram showing a signal of a sheet detection sensor. [Figure 7] 13 is a flowchart showing a full load detection control. [Figure 8] 4 is a flowchart showing a mode selection control. [Figure 9] 4A is a cross-sectional view showing a full-load detection member located at an upper position, and FIG. 4B is a cross-sectional view showing a full-load detection member and a full-load detection sensor located at an upper position. [Figure 10] FIG. 11 is an overall schematic view showing a printer according to a second embodiment. [Figure 11] 4 is a flowchart showing a mode selection control. [Figure 12] 10 is a flowchart showing mode selection control according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <First embodiment> [Overall structure] First, a first embodiment of the present invention will be described. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment may be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied. In other words, the scope of the present invention is not limited to the following embodiment.

[0011] The printer 100 as an image forming apparatus is an electrophotographic laser beam printer that forms a monochrome toner image. As shown in FIG. 1, the printer 100 has a sheet feeding section 1 that feeds stacked sheets, and an image forming section 5 that forms an image on the fed sheets. The printer 100 also has a fixing section 11 that fixes the image transferred to the sheet, a sheet discharge device 12 that can discharge the sheet to the outside of the printer 100, a double-sided conveying section 21, a sheet length detection section 30, and an environment sensor 25. The sheets in this embodiment include paper such as paper and envelopes, plastic films such as overhead projector sheets (OHP), cloth, etc.

[0012] When an image formation command is output to the printer 100, an image forming process is started by the image forming unit 5 based on image information input from an external computer or the like connected to the printer 100. The image forming unit 5 has a laser scanner 8, a photosensitive drum 6, and a charging roller 7, a developing roller 9, and a transfer roller 10 arranged along the photosensitive drum 6. The laser scanner 8 irradiates a laser beam toward the photosensitive drum 6 based on the input image information. At this time, the photosensitive drum 6 is charged in advance by the charging roller 7, and an electrostatic latent image is formed on the photosensitive drum 6 by irradiating it with the laser beam. Thereafter, the electrostatic latent image is developed by the developing roller 9, and a monochrome toner image is formed on the photosensitive drum 6.

[0013] In parallel with the above-mentioned image forming process, sheets S are fed from the sheet feeding section 1. The sheet feeding section 1 has a cassette 41 for stacking sheets S, a pickup roller 42, and a separation roller pair 43. The sheets S stacked in the cassette 41 are fed by the pickup roller 42, and the sheets S fed by the pickup roller 42 are separated one by one by the separation roller pair 43.

[0014] The sheets S separated one by one by the separation roller pair 43 are transported toward the transfer roller 10 by the transport roller pair 44, 45. Then, the toner image on the photosensitive drum 6 is transferred onto the sheet S by the electrostatic load bias applied to the transfer roller 10. The sheet S onto which the toner image has been transferred is applied with predetermined heat and pressure by the pressure roller 11a and heating unit 11b of the fixing section 11, so that the toner is melted and fixed (fixed). The heating unit 11b has a built-in heater. The sheet S that has passed through the fixing section 11 is transported to the sheet discharge device 12.

[0015] The sheet discharge device 12 has a guide member 20, a discharge roller unit 31, a discharge tray 13 as a stacking section, and an extension tray 14. The discharge roller unit 31 has a discharge drive roller 17, a discharge driven roller 18, and a reverse driven roller 19. The discharge drive roller 17 is driven by a motor M (see FIG. 5), and the discharge driven roller 18 and the reverse driven roller 19 rotate following the discharge drive roller 17. In other words, the discharge driven roller 18 and the reverse driven roller 19 are rotated by the discharge drive roller 17. The discharge drive roller 17 and the discharge driven roller 18 form a discharge nip 15, and the discharge drive roller 17 and the reverse driven roller 19 form a reverse nip 16.

[0016] In the case of single-sided printing in which an image is formed on one side of the sheet S, the sheet S conveyed by the fixing unit 11 is guided toward the discharge nip 15 by the guide member 20. The guide member 20 is configured to be rotatable at any timing by an actuator (not shown). The sheet S is then discharged outside the apparatus by the discharge nip 15 and stacked on the discharge tray 13.

[0017] In the case of double-sided printing in which images are formed on both sides of the sheet S, the sheet S with an image formed on the first side is conveyed to the reversing nip 16 by the guide member 20. The discharge driving roller 17 rotates in the reverse direction after the rear end of the sheet S leaves the guide member 20. As a result, the sheet S is switched back by the reversing nip 16 and conveyed toward the double-sided conveying section 21.

[0018] The sheet S conveyed to the double-sided conveying section 21 is conveyed again by the conveying roller pair 21a to the conveying roller pair 45. Then, an image is formed on the second surface of the sheet S by the transfer roller 10, and the sheet S is discharged onto the discharge tray 13 by the discharge nip 15.

[0019] The extension tray 14 is provided on the discharge tray 13 and can be rotated between a stored position indicated by a solid line in Fig. 1 and an extended position indicated by a dashed line in Fig. 1. For example, when discharging a long sheet through the discharge nip 15, the user rotates the extension tray 14 from the stored position to the extended position. This causes the leading edge of the sheet S to be pressed by the extension tray 14 positioned at the extended position, and the sheet S discharged onto the discharge tray 13 can be prevented from falling from the discharge tray 13. The sheet length detection unit 30 and the environment sensor 25 will be described later.

[0020] [Full load detection device] Next, the full-load detection device 22 of the sheet discharge device 12 will be described in detail. As shown in Fig. 2, the sheet discharge device 12 includes a full-load detection device 22 provided to prevent overloading of sheets S on the discharge tray 13. The full-load detection device 22 has a full-load detection member 50 as a movable member and a full-load detection sensor 24 as a detection unit. The full-load detection member 50 has a rotation shaft 51 rotatably supported on the housing 100A of the printer 100, flag portions 23a, 23b, 23c, and 23d, and a light-shielding portion 52.

[0021] The flag portions 23a, 23b, 23c, and 23d are fixed to the rotating shaft 51 and extend in a radial direction perpendicular to the axial direction AD of the rotating shaft 51. The flag portions 23a, 23b, 23c, and 23d are arranged side by side in the axial direction AD, and are arranged symmetrically in the axial direction AD with respect to the center of the conveying path. This allows the flag portions 23a, 23b, 23c, and 23d to come into contact with sheets of various sizes discharged by the discharge nip 15.

[0022] The flag portions 23a, 23b, 23c, and 23d have the same configuration and function as each other, and therefore, in the following description, when the flag portions 23a, 23b, 23c, and 23d are not particularly distinguished from each other, they will be simply referred to as the flag portion 23 and illustrated in the drawings.

[0023] The light-shielding portion 52 is fixed to one end of the rotating shaft 51 in the axial direction AD, and is configured to be able to shield the light path 24c (see FIG. 3(b)) of the full-load detection sensor 24 fixed to the housing 100A. The full-load detection sensor 24 as a detection portion has a light-emitting portion 24a and a light-receiving portion 24b, and is turned ON when the light-receiving portion 24b receives light emitted from the light-emitting portion 24a. In other words, the full-load detection sensor 24, which is composed of, for example, a photointerrupter, changes an output value based on whether the light-receiving portion 24b receives light. The light path 24c is formed between the light-emitting portion 24a and the light-receiving portion 24b. The rotating shaft 51, the flag portions 23a, 23b, 23c, 23d, and the light-shielding portion 52 of the full-load detection member 50 rotate (move) together.

[0024] As shown in FIG. 3(a) and FIG. 4(a), the sheet S discharged by the discharge roller unit 31 is stacked on the discharge tray 13. The flag portion 23 of the full-load detection member 50 is temporarily lifted by the sheet S conveyed by the discharge roller unit 31, and is lowered when the rear end of the sheet passes through the discharge roller unit 31. The state in which the flag portion 23 of the full-load detection member 50 is temporarily lifted by the sheet and then lowered is hereinafter referred to as the lowered state of the flag portion 23. In addition, hereinafter, the sheets stacked on the discharge tray 13 are referred to as stacked sheets. When the height of the stacked sheets is less than a predetermined height, the flag portion 23 of the full-load detection member 50 in the lowered state does not contact the stacked sheets and is located at a standby position as a first position shown in FIG. 3(a). When the flag portion 23 as the contact portion is located at the standby position, as shown in FIG. 3(b), the light shielding portion 52 shields the light path 24c of the full-load detection sensor 24, so that the full-load detection sensor 24 is OFF (light shielding state).

[0025] When the height of the stacked sheets reaches a predetermined height, the upper surface of the topmost stacked sheet abuts against the lowered flag portion 23. The position at which the lowered flag portion 23 abuts against the upper surfaces of the stacked sheets shifts upward as the height of the stacked sheets increases. In other words, the position of the flag portion 23 abutting against the upper surfaces of the stacked sheets shifts from the standby position toward a detection position, which will be described later, as the number of sheets stacked on the discharge tray 13 increases.

[0026] 4(a), that is, when the flag portion 23 is in contact with the upper surface of the top sheet of the fully loaded stack of sheets SS, the flag portion 23 is in the detection position serving as the second position. In other words, the flag portion 23 is in the detection position when it is in contact with the stack of sheets loaded on the discharge tray 13 at a position higher than a predetermined position. In this manner, the fully loaded detection member 50 including the flag portion 23 moves according to the height of the stack of sheets.

[0027] 4(b), when the flag portion 23 is located at the detection position, the light blocking portion 52 does not block the light path 24c of the full-load detection sensor 24, and the full-load detection sensor 24 is ON (light-transmitting state). Before the flag portion 23 reaches the detection position, the light blocking portion 52 blocks the light path 24c of the full-load detection sensor 24, and the full-load detection sensor 24 is OFF (light-blocking state).

[0028] That is, the full-load detection sensor 24 is turned from OFF to ON when the number of stacked sheets SS increases and the full-load detection member 50 reaches the detection position. In the following, when the flag portion 23 is located at the standby position, the full-load detection member 50 is also referred to as being located at the standby position. Similarly, when the flag portion 23 is located at the detection position, the full-load detection member 50 is also referred to as being located at the detection position. In addition, when the flag portion 23 is in the lowered state, the full-load detection member 50 is also referred to as being in the lowered state. In addition, the light shielding portion 52 and the full-load detection sensor 24 may be configured so that when the flag portion 23 is located between the detection position and an upper position (see FIG. 9(a)) described later, the light shielding portion 52 shields the optical path 24c of the full-load detection sensor 24, and before the flag portion 23 reaches the detection position, the light shielding portion 52 does not shield the optical path 24c of the full-load detection sensor 24.

[0029] [Control Block] Fig. 5 is a block diagram showing a control block of the printer 100 according to this embodiment. As shown in Fig. 5, the printer 100 includes a control unit 80. The control unit 80 includes a central processing unit (CPU) 81, a read only memory (ROM) 82, a random access memory (RAM) 83, and a counter 84. Various programs are stored in the ROM 82, and the CPU 81 reads and executes the programs stored in the ROM 82. The RAM 83 is used as a working area for the CPU 81. The counter 84 counts the number of sheets S discharged by the discharge nip 15.

[0030] The input side of the control unit 80 is connected to the full load detection sensor 24, the sheet detection sensor 4, and the environment sensor 25. As shown in FIG. 1, the printer 100 has a sheet length detection unit 30, which has a sheet detection flag 3 movably biased by a spring (not shown), and the sheet detection sensor 4. In this embodiment, the sheet detection flag 3 is disposed downstream of the conveying roller pair 45 in the sheet conveying direction D1, but is not limited to this. In other words, the sheet detection flag 3 may be disposed anywhere as long as it can come into contact with the sheet conveyed on the conveying path.

[0031] When the sheet detection flag 3 is pressed and moved by the leading edge of the conveyed sheet, the sheet detection sensor 4 changes from OFF to ON, as shown in Fig. 6. Also, when the trailing edge of the sheet passes the sheet detection flag 3, the sheet detection flag 3 returns to the standby position by a spring (not shown), and the sheet detection sensor 4 changes from ON to OFF. The length of the sheet in the sheet conveying direction D1 is calculated from the time that the sheet detection sensor 4 is ON and the sheet conveying speed.

[0032] For example, when an A4 size sheet is conveyed, the time when the sheet detection sensor 4 is ON is time T1, and when an A6 size sheet is conveyed, the time when the sheet detection sensor 4 is ON is time T2. By multiplying these times T1 and T2 by the sheet conveying speed, it is possible to detect the length of the sheet (A4 size, A6 size) being conveyed in the sheet conveying direction D1.

[0033] 1, the environmental sensor 25 is disposed inside the printer 100 and detects the ambient humidity. That is, the environmental sensor 25 detects the temperature around the sheet discharge device 12. In this embodiment, the control unit 80 classifies the environment into three environments, a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment, based on the temperature detected by the environmental sensor 25. For example, in this embodiment, a temperature detected by the environmental sensor 25 between 19° C. and 27° C. is defined as a normal temperature and normal humidity environment, a temperature lower than 19° C. is defined as a low temperature and low humidity environment, and a temperature higher than 27° C. is defined as a high temperature and high humidity environment.

[0034] The threshold values ​​for each of these environments are not limited to those described above and may be set appropriately. In the present embodiment, the environments are classified into three environments, normal temperature and normal humidity environment, high temperature and high humidity environment, and low temperature and low humidity environment, based on the temperature detected by the environment sensor 25, but the environments may be classified into less than three environments or into four or more environments.

[0035] In the present embodiment, the environment is classified into three environments, a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment, based on the temperature detected by the environment sensor 25, but the environment sensor 25 may detect humidity instead of temperature. The environment may be classified into three environments, a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment, based on the detected humidity. The environment sensor 25 may detect temperature and humidity, and may classify into three environments, a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment, based on the detected temperature and humidity. Of course, these environments are not limited to the normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment, and may be classified into less than three environments or four or more environments.

[0036] Further, a motor M is connected to the output side of the control unit 80. The motor M drives the discharge drive roller 17 of the discharge roller unit 31. The control unit 80 controls the motor M to control the discharge roller unit 31 as a discharge unit.

[0037] In addition, an operation unit 85 including a liquid crystal panel, physical buttons, etc. is connected to the control unit 80. Through the operation unit 85, a user can specify the type of sheet to be discharged by the discharge nip 60 and the length of the sheet in the sheet conveying direction D1.

[0038] [Full load detection control] Next, the full-load detection control of this embodiment will be described with reference to Fig. 7 to Fig. 9(b). Fig. 7 describes an example of full-load detection control in a job in which images are formed on a plurality of sheets and the sheets are continuously discharged onto the discharge tray 13. Fig. 8 is a flowchart showing mode selection control, which is a subflow of the full-load detection control. As shown in Fig. 7, the control unit 80 first receives a print start command in the standby state and starts printing on the sheet S (step S1).

[0039] Next, the control unit 80 judges whether the full-load detection sensor 24 is ON (step S2). As described above, when the sheets are sequentially discharged to the discharge tray 13 by the discharge nip 15 of the discharge roller unit 31 and the height of the stacked sheets SS increases, the flag portion 23 of the full-load detection member 50 moves from the standby position toward the detection position and an upper position (see FIG. 9(a)) described later. If it is not judged that the full-load detection sensor 24 is ON (step S2: No), the control unit 80 controls the discharge roller unit 31 to continue discharging the sheets S (step S3). Then, the control unit 80 checks whether there is a next discharge command to discharge the sheets S to the discharge tray 13 (step S4). If there is a next discharge command (step S4: Yes), the process returns to step S1. If there is no next discharge command (step S4: No), the process proceeds to step S5 and stops printing (step S5).

[0040] On the other hand, when it is determined that the full load detection sensor 24 is turned ON (step S2: Yes), the control unit 80 executes the mode selection control (step S6). That is, the mode selection control is executed when the full load detection sensor 24 reaches the detection position.

[0041] Here, the thicker and heavier the sheet S discharged by the discharge nip 15 is, the stronger the force pushing out the stacked sheets SS already stacked on the discharge tray 13 tends to be. If the force pushing out the stacked sheets SS is strong, the stacked sheets SS are more likely to fall off the discharge tray 13, and the stackability of the sheets decreases. For this reason, the thinner the sheet S is and the smaller the basis weight is, the more sheets S can be stacked on the discharge tray 13 while maintaining the stackability.

[0042] Furthermore, if the length of the sheets in the sheet conveying direction D1 is longer than a predetermined length, the stacked sheets tend to protrude outside the discharge tray 13 and are likely to be pushed by the next discharged sheet and fall. For this reason, it is preferable that the length of the sheets S does not protrude outside the discharge tray 13 when stacked on the discharge tray 13. In this embodiment, if the sheets S are A4 size or smaller, they will not protrude outside the discharge tray 13. However, if the sheets S are larger than A4 size, they will go over the extension tray 14 on the discharge tray 13 and protrude outside the discharge tray 13. For this reason, if the sheets S are A4 size or smaller in length, more sheets S can be stacked on the discharge tray 13 while maintaining the stackability.

[0043] Furthermore, when the inside of the printer 100 or the surroundings of the sheet discharge device 12 are in a high temperature and humidity environment, the moisture content of the sheet increases, which increases the coefficient of friction, and the force with which the sheet discharged by the discharge nip 15 pushes out the stacked sheets increases. Also, the moisture content of the sheet differs depending on the temperature and humidity of the surrounding environment of the printer 100, and therefore the amount of curl of the sheet also differs. For example, in a low temperature and low humidity environment or a high temperature and high humidity environment, the amount of curl of the sheet increases, so the number of printed sheets before the sheets stacked on the discharge tray 13 reach a certain height decreases. Therefore, in a normal temperature and normal humidity environment, which is favorable for the friction coefficient and curl amount of the sheet, more sheets S can be stacked on the discharge tray 13.

[0044] As described above, the amount (height) of sheets that can be loaded onto the discharge tray 13 varies depending on the type of sheet discharged by the discharge nip 15, the length of the sheet in the sheet conveying direction D1, and the ambient temperature and / or humidity of the sheet discharge device 12.

[0045] Therefore, in this embodiment, by selecting the normal mode or the print extension mode in the mode selection control, it is possible to increase the number of sheets that can be loaded on the discharge tray 13 while maintaining the sheet loading capacity on the discharge tray 13.

[0046] As shown in Fig. 8, when the mode selection control is executed, the control unit 80 judges whether or not the fixing mode is selected (step S21). The fixing mode is a mode in which the user sets the type of sheet, such as thin paper, regular paper, or thick paper, when printing, thereby appropriately controlling the temperature of the fixing unit 11. In this embodiment, in the fixing mode, the user can specify the type of sheet, for example, via an external PC connected to the printer 100 or the operation unit 85.

[0047] If it is determined that the fixing mode is not selected (step S21: No), the normal mode is set (step S26). In the normal mode, if the full-load detection sensor 24 is ON for a predetermined time or more, it is determined that the stacked sheets SS on the discharge tray 13 are full, and printing is stopped. That is, in the normal mode as the first mode, when the full-load detection sensor 24 detects that the full-load detection member 50 has reached the detection position, the control unit 80 restricts the discharge roller unit 31 from discharging the sheets S. This maintains the stackability of the sheets stacked on the discharge tray 13, and prevents the sheets from falling off the discharge tray 13 or jamming due to overloading.

[0048] On the other hand, if it is determined that the fixing mode is selected (step S21: Yes), the control unit 80 determines whether the type of sheet specified in the fixing mode is a predetermined type. In this embodiment, the control unit 80 determines whether the type of sheet specified in the fixing mode is plain paper or thin paper (step S22). As an example, plain paper has a basis weight of, for example, 64 to 105 g / m 2 Thin paper is a sheet with a basis weight of, for example, 64 g / m 2 For example, a cardboard sheet is 105 g / m 2 If it is determined that the type of the sheet S to be discharged is not plain paper or thin paper (step S22: No), the normal mode is set (step S26).

[0049] If it is determined that the type of the discharged sheet S is plain paper or thin paper (step S22: Yes), the control unit 80 determines whether the length of the discharged sheet S in the sheet transport direction D1 is equal to or less than a predetermined length. In this embodiment, the control unit 80 determines whether the length of the discharged sheet S in the sheet transport direction D1 is equal to or less than A4 size (step S23). The length of the discharged sheet S in the sheet transport direction D1 is detected by the sheet length detection unit 30 as described in FIG. 6. If it is determined that the length of the discharged sheet S is greater than A4 size (step S23: No), the normal mode is set (step S26).

[0050] When it is determined that the length of the discharged sheet S in the sheet conveying direction D1 is equal to or less than A4 size (step S23: Yes), the control unit 80 determines whether or not the environment is a predetermined environment. In the present embodiment, the control unit 80 determines whether or not the surrounding environment is a normal temperature and normal humidity environment based on the detection result of the environment sensor 25 (step S24). When it is determined that the surrounding environment is not a normal temperature and normal humidity environment but a low temperature and low humidity environment or a high temperature and high humidity environment (step S24: No), the normal mode is set (step S26). When it is determined that the surrounding environment is a normal temperature and normal humidity environment (step S24: Yes), the print extension mode is set (step S25).

[0051] When the mode selection control in step S6 of the flowchart in FIG. 7 ends, the control unit 80 proceeds to step S7. In step S7, the control unit 80 judges whether or not the printing extension mode is set (step S7). If the printing extension mode is not set and the normal mode is set (step S7: No), printing is stopped (step S5). That is, the control unit 80 restricts the discharge roller unit 31 from discharging the sheet S when the full-load detection sensor 24 is turned ON.

[0052] On the other hand, if the printing extension mode is set (step S7: Yes), the control unit 80 judges whether or not the predetermined number of sheets equivalent to the extension printable number have been printed by the discharge roller unit 31 after the full-load detection sensor 24 detects that the full-load detection member 50 has reached the detection position (step S8). Note that in this embodiment, the extension printable number is set to a fixed number of 60 sheets, but is not limited to this. For example, the extension printable number may be changed within a range in which the sheets S do not fall off the discharge tray 13 or jam.

[0053] In the extended printing mode, the number of sheets discharged by the discharge roller unit 31 after the full-load detection member 50 reaches the detection position (hereinafter, referred to as the extended printing number) is counted by a counter 84 of the control unit 80. The extended printing number counted by the counter 84 is stored, for example, in the RAM 83, and remains stored in the RAM 83 until the printer 100 is turned off.

[0054] If it is determined that the extended printable number of sheets has not been printed (step S8: No), the control unit 80 determines whether or not it has received a print command for sheets with conditions other than the conditions for selecting the extended printing mode described in steps S22 to S23 of Figure 8 (step S9).

[0055] If a print command for sheets with different conditions has not been received (step S9: No), the process returns to step S8. If the extended printable number of sheets has been printed in step S8 (step S8: Yes) or if a print command for sheets with different conditions has been received (step S9: Yes), printing is stopped (step S5). That is, in the print extension mode, after the full-load detection sensor 24 detects that the full-load detection member 50 has reached the detection position, the control unit 80 restricts the discharge of the sheets S by the discharge roller unit 31 after the full-load detection member 50 has discharged the extended printable number of sheets to the discharge tray 13 by the discharge roller unit 31.

[0056] 9(a)(b) are cross-sectional views showing the full-load detection member 50 and the full-load detection sensor 24 at the upper position after the extended printable number of sheets (60 sheets in this embodiment) have been printed. As shown in FIG. 9(a)(b), the full-load detection member 50 can move to an upper position that is farther away from the standby position than the detection position after reaching the detection position. That is, the full-load detection member 50 transitions from the standby position to the detection position and to the upper position in this order as the height of the stacked sheets SS stacked on the discharge tray 13 increases. Even when the full-load detection member 50 is at the upper position shown in FIG. 9(a)(b), the light shielding portion 52 does not shield the light path 24c of the full-load detection sensor 24, and the full-load detection sensor 24 is ON. As described above, in the printing extension mode as the second mode, the discharge roller unit 31 is allowed to discharge the sheets S even when the full-load detection member 50 is located between the detection position and the upper position until the extended printable number of sheets reaches the extended printable number. In other words, in the second mode, the extended printing mode, the discharge roller unit 31 can continue to discharge the sheet S even when the full load detection member 50 is positioned between the detection position and the upper position until the extended printing number reaches the above-mentioned extended printing possible number.

[0057] After printing is stopped in step S5, the control unit 80 determines whether the stack of sheets SS stacked on the discharge tray 13 has been removed by the user (step S10). The control unit 80 determines that the stack of sheets SS has been removed by the user based on the full-load detection sensor 24 changing from ON to OFF. If it is determined that the stack of sheets SS has been removed by the user (step S10: Yes), the control unit 80 returns to the standby state.

[0058] As described above, in this embodiment, when the full-load detection sensor 24 detects that the full-load detection member 50 has reached the detection position, the control unit 80 controls the discharge roller unit 31 in the normal mode or the print extension mode. When the full-load detection member 50 retreats from the standby position and moves to the detection position, the output of the full-load detection sensor 24 changes from the first output (OFF) to the second output (ON). When the output of the full-load detection sensor 24 is the second output, the control unit 80 determines that the full-load detection member 50 has reached the detection position. Then, in a state in which the output of the full-load detection sensor 24 is the second output, the control unit 80 controls the discharge roller unit 31 in the normal mode or the print extension mode. Then, the control unit 80 selects the normal mode or the print extension mode based on the type of sheet discharged by the discharge roller unit 31, the length of the sheet in the sheet conveying direction D1, and the temperature and humidity environment around the sheet discharge device 12. When the printing extension mode is selected, the discharge roller unit 31 can continue to discharge the sheet S until the number of extended print sheets reaches the number of extended printable sheets, thereby increasing the number of sheets that can be loaded onto the discharge tray 13.

[0059] Moreover, whether the normal mode or the print extension mode is selected, the stackability of the sheets stacked on the discharge tray 13 can be maintained, so that the sheets S can be prevented from falling off the discharge tray 13 or from jamming.

[0060] <Second embodiment> Next, a second embodiment of the present invention will be described, which is the same as the first embodiment except that a media sensor 86 is added. Therefore, the same configuration as the first embodiment will be omitted from the illustrations or will be described by using the same reference numerals in the drawings.

[0061] In the first embodiment, in the mode selection control shown in FIG. 8, the type of sheet specified in the fixing mode is used to determine whether to set the print extension mode. In contrast, the printer 200 according to the second embodiment uses a sensor capable of detecting the type of sheet S to determine the type of sheet S, as shown in FIG. 10. In this embodiment, the printer 200 uses a media sensor 26 capable of detecting the thickness of the sheet S to determine the type of sheet S. The media sensor 26 is composed of two phototransistors that respectively detect, for example, reflected light irradiated from a light source onto the sheet and reflected by the sheet, and transmitted light irradiated from the light source onto the sheet and transmitted through the sheet. The media sensor 26 may also be an ultrasonic sensor.

[0062] 10, in the present embodiment, the media sensor 26 is disposed between the separation roller pair 43 and the conveying roller pair 44 in the sheet conveying direction D1, but is not limited thereto. For example, the media sensor 26 may detect the thickness of the conveyed sheet S downstream of the conveying roller pair 44 in the sheet conveying direction D1.

[0063] Fig. 11 is a flow chart showing mode selection control according to the second embodiment, and is different from Fig. 10 in that step S21 is omitted. The main flow of full load detection control (see Fig. 7) is the same as that of the first embodiment. In step S22, the control unit 80 determines whether the sheet S is a plain paper or a thin paper based on the thickness of the sheet S detected by the media sensor 26 (step S22).

[0064] As described above, in this embodiment, by using the media sensor 26, the user does not need to select the type of sheet, such as thin paper, regular paper, or thick paper, thereby improving usability.

[0065] In the present embodiment, the media sensor 26 detects the thickness of the sheet S, but is not limited to this. For example, the media sensor 26 may detect the basis weight, surface roughness, or glossiness of the sheet S, and the control unit 80 may determine whether or not to set the extended print mode based on the detection result of the media sensor 26.

[0066] <Third embodiment> Next, a third embodiment of the present invention will be described, which is a modification of the mode selection control of the first embodiment. Therefore, the same configurations as those of the first embodiment will be omitted from the drawings or will be described by using the same reference numerals in the drawings.

[0067] In the first and second embodiments, the number of sheets that can be printed by extension is a fixed number. In contrast, in the present embodiment, the number of sheets that can be printed by extension is determined according to the type of sheet discharged by the discharge roller unit 31, the length of the sheet in the sheet conveying direction D1, and the temperature and humidity conditions around the sheet discharge device 12. n is determined.

[0068] Fig. 12 is a flowchart showing the mode selection control according to the third embodiment. The main flow of the full load detection control (see Fig. 7) is the same as that of the first embodiment. As shown in Fig. 12, when the mode selection control is executed, the control unit 80 judges whether or not the fixing mode is selected (step S21). If it is judged that the fixing mode is not selected (step S21: No), the normal mode is set (step S26).

[0069] On the other hand, if it is determined that the fixing mode is selected (step S21: Yes), the control unit 80 determines the type of the sheet S to be discharged based on the sheet type specified in the fixing mode (step S31). In this embodiment, the types of the sheets S are classified into three types: thin paper, regular paper, and thick paper, but are not limited thereto and may be classified into two or more types.

[0070] For example, if the type of sheet is plain paper (step S31: plain paper), the control unit 80 determines the length of the sheet in the sheet conveying direction D1 (step S32). The length of the sheet is detected by the sheet length detection unit 30 (see FIG. 1). In the present embodiment, the lengths of the sheets are classified into three types, LTR size, A4 size, and A5 size, but other sizes such as LGL size and B5 size may also be included in the classification, and it is sufficient that the lengths are classified into two or more types.

[0071] For example, when the length of the sheet is A4 size (step S32: A4 size), the control unit 80 judges the surrounding temperature and humidity environment (step S33) based on the environment sensor 25. In this embodiment, the surrounding temperature and humidity environment is classified into three environments, a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment, but it may be classified into two or more environments.

[0072] When it is determined that the surrounding temperature and humidity environment is a low-temperature and low-humidity environment (step S33: low-temperature and low-humidity environment), the control unit 80 sets the extended printable number of sheets to X 1 When it is determined that the ambient temperature and humidity environment is a normal temperature and humidity environment (step S33: normal temperature and humidity environment), the control unit 80 sets the extended printable number of sheets to X 2 When it is determined that the ambient temperature and humidity environment is a high temperature and high humidity environment (step S33: high temperature and high humidity environment), the control unit 80 sets the extended printable number of sheets to X 3 The number of sheets is set to one (step S36).

[0073] After steps S33 to S36, the control unit 80 sets the printing extension mode (step S25) and ends the mode selection control. Although not described above, even if the type of sheet is determined to be thin paper in step S31 (step S31: thin paper) or the type of sheet is determined to be thick paper (step S31: thick paper), the extension printable number is set based on the conditions in steps S32 and S33. That is, in this embodiment, there are 3×3×3=27 patterns of sheet types, sheet lengths, and surrounding environments, and the extension printable number is set for each of them. In this embodiment, in the printing extension mode as the second mode, the discharge roller unit 31 can continue to discharge the sheets S until the extension printable number reaches the extension printable number, even if the full-load detection member 50 is located between the detection position and the upper position.

[0074] As described above, in this embodiment, the characteristics of the sheet S and the influence of the surrounding environment can be taken into consideration in more detail, and the number of sheets that can be stacked on the discharge tray 13 can be increased.

[0075] In the mode selection control of the present embodiment, first, it is determined whether or not the fixing mode is selected, but the present invention is not limited to this. For example, as in the second embodiment, step S21 may be omitted and the type of sheet may be determined using the media sensor 26.

[0076] <Other embodiments> In any of the above-described embodiments, either the normal mode or the extended printing mode is selected based on the type of sheet discharged by the discharge nip 15, the length of the sheet in the sheet transport direction D1, and the temperature and / or humidity around the sheet discharge device 12. However, this is not limiting. For example, either the normal mode or the extended printing mode may be selected based on at least one of the type of sheet discharged by the discharge nip 15, the length of the sheet in the sheet transport direction D1, and the temperature and / or humidity around the sheet discharge device 12.

[0077] In addition, in any of the above-described embodiments, the full load detection sensor 24 is configured as a photointerrupter having the light emitting portion 24a and the light receiving portion 24b, but is not limited to this. For example, the full load detection sensor 24 may be a sensor such as a switch whose output value changes when pressed by the full load detection member 50.

[0078] In addition, in any of the above-described embodiments, the fully loaded detection member 50 is configured to be rotatable about the rotation shaft 51, but this is not limited thereto. For example, the fully loaded detection member 50 may be configured to be slidable in the vertical direction.

[0079] In addition, in any of the above-described embodiments, the sheet S is discharged to the discharge tray 13 by the discharge roller unit 31, but this is not limiting. For example, instead of the discharge roller unit 31, a pair of discharge rollers that discharge the sheet S to the discharge tray 13 and a pair of reversing rollers that reverse the sheet S toward the double-sided conveying section 21 may be separately provided. In addition, in the case of a configuration in which double-sided printing is not performed, instead of the discharge roller unit 31, only a pair of discharge rollers that discharge the sheet S to the discharge tray 13 may be provided.

[0080] In addition, in any of the above-described embodiments, the mode selection control (step S6) is executed after step S2, but this is not limited to this. For example, the mode selection control (step S6) may be executed before step S2.

[0081] In addition, in each of the above-mentioned embodiments, the electrophotographic printer 100 has been used as an example of an image forming apparatus, but the present invention is not limited thereto. The image forming apparatus includes a printer, a copier, a facsimile, and a multifunction machine, and refers to an apparatus that forms an image on a sheet used as a recording medium based on image information input from an external PC or image information read from an original. In addition, an image forming apparatus may be connected to an accessory device such as an optional feeder, an image reader, and a sheet processing device in addition to a main body having an image forming function, and the entire system to which such accessory devices are connected is also a type of image forming apparatus.

[0082] In addition, in this embodiment, a direct transfer type image forming unit 5 that directly transfers from the photosensitive drum 6 to the sheet S is used, but the present invention is not limited to this. For example, an intermediate transfer type image forming unit may be used that performs primary transfer of a toner image from the photosensitive drum to an intermediate transfer body, and then secondary transfer of the toner image from the intermediate transfer body to the sheet S. In addition, the image forming unit 5 may be configured to be capable of forming an image by superimposing toner images formed on a plurality of photosensitive drums using toners of different colors on the sheet.

[0083] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0084] The disclosure of the present embodiment also includes the following configuration examples and method examples. (Configuration 1) a discharge section for discharging the sheet; a stacking section for stacking the sheets discharged by the discharge section; a movable member capable of contacting the sheets loaded on the loading section, the movable member being movable to a first position, a second position, and a third position that is farther away from the first position than the second position; A detection unit that detects a position of the moving member; A control unit that controls the discharge unit, the movable member moves from the first position toward the second position and the third position as the height of the sheets stacked on the stacking section increases, the control unit controls the discharge unit in a first mode in which, when the detection unit detects that the moving member has reached the second position, the discharge unit is restricted from discharging the sheet, and in a second mode in which the discharge unit is allowed to continue discharging the sheet even when the moving member is positioned between the second position and the third position. A sheet discharging device comprising: (Configuration 2) In the second mode, after the detection unit detects that the moving member has reached the second position and a predetermined number of sheets are discharged to the stacking unit by the discharge unit, discharge of the sheets by the discharge unit is restricted. 2. The sheet ejection device according to configuration 1. (Configuration 3) the control unit selects either the first mode or the second mode depending on at least one of a type of sheet discharged by the discharge unit, a length of the sheet in a sheet conveying direction, and an ambient temperature and / or humidity of the sheet discharge device. 3. The sheet ejection device according to configuration 1 or 2. (Configuration 4) an operation unit that allows a user to specify a type of sheet to be discharged by the discharge unit; a sheet length detection unit that detects the length of the sheet in the sheet conveying direction; and an environmental sensor for detecting the temperature and / or humidity around the sheet ejection device. 4. The sheet ejection device according to configuration 3. (Configuration 5) a media sensor that detects the type of sheet discharged by the discharge unit; a sheet length detection unit that detects the length of the sheet in the sheet conveying direction; and an environmental sensor for detecting the temperature and / or humidity around the sheet ejection device. 4. The sheet ejection device according to configuration 3. (Configuration 6) The predetermined number is constant. 3. The sheet ejection device according to configuration 2. (Configuration 7) the control unit determines the predetermined number of sheets according to each condition, including a type of sheet discharged by the discharge unit, a length of the sheet in a sheet conveying direction, and an ambient temperature and / or humidity of the sheet discharge device. 3. The sheet ejection device according to configuration 2. (Configuration 8) The detection unit has a light emitting unit that emits light and a light receiving unit that receives the light emitted from the light emitting unit, the moving member has a contact portion capable of contacting the sheets loaded on the stacking portion, and a light blocking portion that moves integrally with the contact portion and is capable of blocking light emitted from the light emitting portion toward the light receiving portion, 8. The sheet ejection device according to any one of configurations 1 to 7. (Configuration 9) The movable member is rotatable around a rotation axis from the first position toward the second position and the third position. 9. The sheet ejection device according to any one of configurations 1 to 8. (Configuration 10) When the height of the sheets stacked on the stacking section is less than a predetermined height, the moving member does not come into contact with the sheets stacked on the stacking section at the first position. 10. The sheet ejection device according to any one of configurations 1 to 9. (Configuration 11) an image forming unit that forms an image on a sheet; a discharge section that discharges a sheet on which an image has been formed by the image forming section; a stacking section for stacking the sheets discharged by the discharge section; a movable member capable of contacting the sheets loaded on the loading section, the movable member being movable to a first position, a second position, and a third position that is farther away from the first position than the second position; A detection unit that detects a position of the moving member; A control unit that controls the discharge unit, the movable member moves from the first position toward the second position and the third position as the height of the sheets stacked on the stacking section increases, the control unit controls the discharge unit in a first mode in which, when the detection unit detects that the moving member has reached the second position, the discharge unit is restricted from discharging the sheet, and in a second mode in which the discharge unit is allowed to continue discharging the sheet even when the moving member is positioned between the second position and the third position. 1. An image forming apparatus comprising: [Explanation of symbols]

[0085] 5: image forming unit / 12: sheet discharge device / 13: loading unit (discharge tray) / 23: contact unit (flag unit) / 24: detection unit (full-load detection sensor) / 24a: light-emitting unit / 24b: light-receiving unit / 25: environment sensor / 26: media sensor / 30: sheet length detection unit / 31: discharge unit (discharge roller unit) / 50: moving member (full-load detection member) / 51: rotating shaft / 52: light-shielding unit / 80: control unit / 85: operation unit / 100, 200: image forming device (printer) / D1: sheet transport direction

Claims

1. a discharge unit that discharges the sheet; a stacking section for stacking the sheets discharged by the discharge section; a movable member that can come into contact with the sheets stacked on the stacking section and that can move to a first position, a second position, and a third position that is farther from the first position than the second position; a detection unit that detects the position of the moving member; a control unit that controls the discharge unit, the moving member moves from the first position toward the second position and the third position as the height of the sheets stacked on the stacking section increases, the control unit controls the discharge unit in a first mode in which, when the detection unit detects that the moving member has reached the second position, the discharge unit is restricted from discharging the sheet, or in a second mode in which the discharge unit is allowed to continue discharging the sheet even when the moving member is positioned between the second position and the third position; the control unit, in the second mode, regulates discharge of sheets by the discharge unit after the detection unit detects that the moving member has reached the second position and after the discharge unit discharges a predetermined number of sheets to the stacking unit; the control unit controls the discharge unit in the second mode when a type of the sheet discharged by the discharge unit is a predetermined type, when a length of the sheet in a sheet conveying direction is shorter than a predetermined length, and when a temperature of the sheet is within a predetermined range; the control unit controls the discharge unit in the first mode when at least one of the following conditions is not satisfied: the type of the sheet discharged by the discharge unit is the predetermined type, the length of the sheet in the sheet conveying direction is shorter than the predetermined length, and the temperature is within the predetermined range. A sheet discharge device characterized by:

2. an operation unit that allows a user to specify the type of sheet to be discharged by the discharge unit; a sheet length detection unit that detects the length of the sheet in the sheet conveying direction; an environmental sensor that detects the temperature, 2. The sheet ejection device according to claim 1.

3. a media sensor that detects the type of the sheet discharged by the discharge unit; a sheet length detection unit that detects the length of the sheet in the sheet conveying direction; an environmental sensor that detects the temperature, 2. The sheet ejection device according to claim 1.

4. the detection unit has a light-emitting unit that emits light and a light-receiving unit that receives the light emitted from the light-emitting unit, The moving member has a contact portion that can contact the sheets stacked on the stacking portion, and a light-shielding portion that moves integrally with the contact portion and can block light emitted from the light-emitting portion toward the light-receiving portion.

2. The sheet ejection device according to claim 1.

5. the movable member is rotatable around a rotation axis from the first position toward the second position and the third position; 2. The sheet ejection device according to claim 1.

6. When the height of the sheets stacked on the stacking section is less than a predetermined height, the moving member does not come into contact with the sheets stacked on the stacking section at the first position.

2. The sheet ejection device according to claim 1.

7. an image forming unit that forms an image on a sheet; a discharge section that discharges a sheet on which an image has been formed by the image forming section; a stacking section for stacking the sheets discharged by the discharge section; a movable member that can come into contact with the sheets stacked on the stacking section and that can move to a first position, a second position, and a third position that is farther from the first position than the second position; a detection unit that detects the position of the moving member; a control unit that controls the discharge unit, the moving member moves from the first position toward the second position and the third position as the height of the sheets stacked on the stacking section increases, the control unit controls the discharge unit in a first mode in which, when the detection unit detects that the moving member has reached the second position, the discharge unit is restricted from discharging the sheet, or in a second mode in which the discharge unit is allowed to continue discharging the sheet even when the moving member is positioned between the second position and the third position; the control unit, in the second mode, regulates discharge of sheets by the discharge unit after the detection unit detects that the moving member has reached the second position and after the discharge unit discharges a predetermined number of sheets to the stacking unit; the control unit controls the discharge unit in the second mode when a type of the sheet discharged by the discharge unit is a predetermined type, when a length of the sheet in a sheet conveying direction is shorter than a predetermined length, and when a temperature of the sheet is within a predetermined range; the control unit controls the discharge unit in the first mode when at least one of the following conditions is not satisfied: the type of the sheet discharged by the discharge unit is the predetermined type, the length of the sheet in the sheet conveying direction is shorter than the predetermined length, and the temperature is within the predetermined range. An image forming apparatus characterized by:

Images